The central noradrenergic system has been implicated in the regulation of cerebral microcirculation; first on the basis of anatomical localization of dopamine-beta-hydroxylase containing nerve fibers on small blood vessels and secondly by demonstrating effects on cerebral blood flow and capillary permeability by intraventricular administration of the alpha-adrenergic blocker phentolamine and by stimulation of the locus coeruleus. This work has been done in monkeys. We propose to extend the above observations using electrical stimulation and other pharmacological agents known to effect the central noradrenergic system. A rat model is being developed that will permit indirect evaluation of cerebral blood flow and vascular permeability so that many of the experimental results can be confirmed in a different species. Dopamine-beta-hydroxylase enzyme activity and histochemical localization will be utilized to further evaluate the effect of centrally administered 6-OH dopamine. BIBLIOGRAPHIC REFERENCES: Raichle, M.E., Hartman, B.K., Eichling, J.O., Sharpe, L.G. Central catecholamines and microcirculation central noradrenergic regular of cerebral blood flow and vascular permeability. Proc. Nat. Acad. Sci. Vol. 72 (9): pp. 3726-3730, Sept. 1975. Swanson, L.W., Hartman, B.K. The central adrenergic system. An immunofluorescence study of the location of cell bodies and their efferent connections in the rat utilizing dopamine-beta-hydroxylase as a marker. J. Comp. Neur. 163: pp. 467-506, 1975.